1. Technical Field
The present invention relates to an active phased array antenna and an antenna controlling apparatus and, more particularly, to an active phased array antenna which receives and transmits a microwave in a communication equipment such as a wireless for mobile object identification equipment or a satellite broadcast receiving apparatus, as well as an active phased array antenna which receives and transmits millimeter waves employed in such as a collision preventing radar for automobiles, and also to an antenna controlling apparatus employed for controlling these active phased array antennas.
2. Background Art
Conventionally, a so-called active phased array antenna is generally used as an antenna which receives and transmits microwaves and millimeter waves.
This active phased array antenna conventionally used will be described with reference to figures.
FIG. 10(a) is a diagram schematically illustrating a construction of a conventional active phased array antenna 100, and FIG. 10(b) exemplifies the construction of a phase shifter 707 as an element constituting the active phased array antenna 100.
The conventional active phased array antenna 100 includes plural antenna patches 706a-706p arrayed on a dielectric substrate and a feeding line 710 for distributing a high-frequency signal applied to a feeding terminal 711 to respective antenna patches 706. The active phased array antenna 100 also includes phase shifters 707a-707p corresponding to respective antenna patches 706 which are arranged on the feeding line 710 and changes a phase of the high-frequency signal passing therethrough and a control circuit 708 which applies a desired dc control voltage to each phase shifter 707 and controls a phase shift of the high-frequency signal passing each phase shifter 707. While sixteen antenna patches 706 and sixteen phase shifters 707 are provided, respectively, in FIG. 10, this is only an example.
Further, FIG. 10(b) is a diagram illustrating the construction of the phase shifter 707 used in the active phased array antenna 100. All the phase shifters 707 have the identical constructions.
The phase shifter 707 includes first transmission lines 14a and 20a at an input side and an output side which are connected to the feeding line 710 as transmission lines that transmit inputted high-frequency signals, second transmission lines 14b and 20b at the input side and the output side which are connected to a dc power source through high-frequency blocking elements 21 and 27, an intermediate transmission line 17 which is connected to a dc power source through a high-frequency blocking element 24, a first and a second transmission lines for switching 15 and 16 of different lengths which are connected to a first control line V1 and a first inversion control line NV1 through the high-frequency blocking element 24, respectively, and a third and a fourth transmission lines for switching 18 and 19 of different lengths which are connected to a second control line V2 and a second inversion control line NV2 through high-frequency blocking elements 25 and 26, respectively.
A dc blocking element 12 which blocks a direct current is connected between the first transmission line 14a and the second transmission line 14b at the input side, and a blocking element 13 which blocks a direct current is connected between the first transmission line 20a and the second transmission line 20b at the output side, respectively.
Further, the first and the second transmission lines for switching 15 and 16 are located between the intermediate transmission line 17 and the second transmission line 14b at the input side.
Connected between an input side end of the first transmission line for switching 15 and an output side end of the second transmission line 14b at the input side is a PIN diode 31a connected in a forward direction viewed from the second transmission line 14b to the first transmission line for switching 15, and between an output side end of the first transmission line for switching 15 and an input side end of the intermediate transmission line 17 is a PIN diode 31b connected in a forward direction viewed from the intermediate transmission line 17 to the first transmission line for switching 15, respectively.
Connected between an input side end of the second transmission line for switching 16 and an output side end of the second transmission line 14b at the input side is a PIN diode 32a connected in a forward direction viewed from the second transmission line 14b to the second transmission line for switching 16, and connected between an output side end of the second transmission line for switching 16 and an input side end of the intermediate transmission line 17 is a PIN diode 32b connected in a forward direction viewed from the intermediate transmission line 17 to the second transmission line for switching 16.
Further, the third and the fourth transmission lines for switching 18 and 19 are located between the intermediate transmission line 17 and the second transmission line 20b at the output side.
Connected between an input side end of the third transmission line for switching 18 and an output side end of the intermediate transmission line 17 is a PIN diode 33a connected in a forward direction viewed from the intermediate transmission line 17 to the third transmission line for switching 18, and connected between an output side end of the third transmission line for switching 18 and an input side end of the second transmission line 20b at the output side is a PIN diode 33b connected in a forward direction viewed from the second transmission line 20b to the third transmission line for switching 18.
Connected between an input side end of the fourth transmission line for switching 19 and an output side end of the intermediate transmission line 17 is a PIN diode 34a connected in a forward direction viewed from the intermediate transmission line 17 to the fourth transmission line for switching 19, and connected between an output side end of the fourth transmission line for switching 19 and an input side end of the second transmission line 20b at the output side is a PIN diode 34b connected in a forward direction viewed from the second transmission line 20 to the fourth transmission line for switching 19.
The operation of the active phased array antenna which is provided with the so-constructed phase shifters 707 will be described.
When a high-frequency electric power is applied to the feeding terminal 711, the high-frequency electric power is supplied to respective antenna patches 706 through respective phase shifters 707. Then, a corresponding control voltage required is applied to each phase shifter 707, and a processing of making the phase of the high-frequency electric power advanced or delayed by a prescribed phase shifter is performed at each phase shifter 707 on the basis of the control voltage from the control circuit 708. Thereby, the high-frequency electric powers of the prescribed positions are inputted from respective antenna patches 706.
In this way, the active phased array antenna 100 performs a control of its orientation characteristics by applying a dc control voltage from the control circuit 708 to respective phase shifters 707 to change the phase shift quantity.
Next, the operation of the phase shifter will be described.
The high-frequency electric power supplied to the phase shifter 707 through the feeding line 710 passes through sequentially the first transmission line 14a at the input side, the dc blocking element 12, the second transmission line 14b at the input side, either one of the first and the second transmission lines for switching 15 and 16, the intermediate transmission line 17, either one of the third and the fourth transmission lines for switching 18 and 19, the second transmission line 20b at the output side, the dc blocking element 13, and the first transmission line 20a at the output side, and is propagated to the antenna patch 706.
Then, a control voltage for switching ON/OFF of the corresponding PIN diodes 31, 32, 33, and 34 is applied from the respective control lines V1, V2, NV1, and NV2 to respective transmission lines 15, 16, 18, and 19, so that respective PIN diodes 31, 32, 33, ad 34 are switched ON/OFF according to the control voltage. Thereby, the length of the transmission line through which the high-frequency electric power passes in the phase shifter 707 is changed, and the high-frequency electric power is outputted with its phase advanced or delayed by the prescribed phase shift.
However, in the conventional phase shifter 707 having the above-described construction which constitutes the prior art active phased array antenna 100, since the internal transmission lines are switched by a control voltage to change a phase shift, the phase shift is performed not successively but step by step, and this made it necessary to provide a circuit construction for switching transmission lines corresponding to the stage number (step number), i.e., that including transmission lines for switching, high-frequency blocking elements, control lines, and the like.
In other words, there exists a problem in that a construction which enables performing a phase shift with fine steps as well as obtaining a large phase shift, a large number of circuit constructions for switching transmission lines are required.
Further, also in a case where a large number of antenna patches are provided to obtain an antenna with a large gain, there is a problem that the circuit construction and wirings constituting the phase shifter are complicated.
Further, as a phase shifter employed for the conventional active phased array antenna, there is also one combining a varactor diode with a microstrip hybrid coupler. Though the varactor diode can continuously change orientation, it has a low control voltage, i.e., of several volts because it utilizes a junction capacitance of a PN junction, and therefore, when a passing electric power of a high-frequency signal which passes through the phase shifter is high, the junction capacitance would change by the signal voltage, resulting in that a lot of higher harmonics are generated. Therefore, it was not general to employ a phase shifter having such a construction.
Further, while dielectric substrate materials of the microstrip structure control the high frequency propagation characteristics as well as supports antenna patches or feeding line conductors, the dielectric materials are required to have as its high-frequency characteristics that of small loss and stable dielectric constant when materials having these characteristics are employed as dielectric materials, a problem arises that a larger portion of the antenna cost is occupied thereby.
The present invention is made to solve the above-mentioned problems and has for its object to provide a low cost active phased array antenna, and an antenna controlling apparatus, which is of simpler structure and capable of continuously changing antenna orientation characteristics.
According to Claim 1 of the present invention, there is provided an active phased array antenna which has a structure in which plural antenna patches and a feeding terminal for applying a high-frequency electric power to a dielectric substrate are provided on the dielectric substrate, the respective antenna patches and the feeding terminal are connected by feeding lines branching off from the feeding terminal, and a phase shifter which can electrically change the phase of a high-frequency signal passing on the respective feeding lines are arranged to constitute a part of the feeding lines, and the phase shifter comprises a microstrip hybrid coupler which employs paraelectrics as base material and a microstrip stab which employs ferroelectrics as base material and which is electrically connected to the microstrip hybrid coupler, and a dc control voltage is applied to the microstrip stab to change the passing phase shift quantity.
Therefore, by changing a control voltage, the passing phase shift quantity can be changed successively, and further, a phase shifter and a feeding line can be constituted by a single conductor layer, whereby it is possible to supply a control voltage to plural phase shifters through a single control line, thereby simplifying a wiring.
According to Claim 2 of the present invention, there is provided an active phased array antenna as defined in Claim 1, wherein the plural antenna patches are arranged in matrix at equal intervals in the row and column directions respectively, the phase shifters are arranged so that the number of the phase shifters inserted between each antenna patch in each row and the feeding terminal is larger by one sequentially than the number of the phase shifters inserted between each antenna patch in adjacent row and the feeding terminal, and so that the number of the phase shifters inserted between each antenna patch in each column and the feeding terminal is larger by one sequentially than the number of the phase shifters inserted between each antenna patch in adjacent column and the feeding terminal, and all the phase shifters have the same characteristics in the row and column directions respectively.
Therefore, it is possible to control antenna the orientation characteristics of an antenna regardless of the number of antenna patches only by changing a control voltage applied from the both end sides of a control line to which plural phase shifters are connected.
According to Claim 3 of the present invention, there is provided an active phased array antenna as defined in Claim 1 or 2, wherein the active phased array antenna is constructed by laminating seven layers, which seven layers comprises a first layer, a second layer, . . . , a seventh layer sequentially from the top layer, and the first, third, fifth, and seventh layer comprise dielectric material, while the second, fourth, and sixth layer comprise conductor, and further, the active phased array antenna has a first microstrip structure comprising the first, second, third, and fourth layer, and a second microstrip structure comprising the fourth, fifth, sixth, and seventh layer and the first microstrip structure and the above-mentioned second microstrip structure share the fourth layer as a grounded layer, and further, the antenna patch is provided in the second layer, the feeding line and the phase shifter are provided in the sixth layer, air is employed in the third layer, and a combination of air and the ferroelectrics is employed in the fifth layer.
Therefore, as a dielectric material between conductor layers of the microstrip structure, air which causes a significantly small loss of a high-frequency electric power and has a stable dielectric constant is used, and as a dielectric base material outside the surface of the feeding line conductor layer, a dielectric member which supports an antenna patch and a feeding line conductor is used, whereby they may also serve as protective layers at the antenna surface, resulting in a low cost device with a simple structure.
According to Claim 4 of the present invention, there is provided an active phased array antenna which is provided with a phase shifter that comprises at least an open end stab having ferroelectrics and ferromagnetic materials as base materials, and a microstrip hybrid coupler having paraelectrics as base materials.
According to Claim 5 of the present invention, there is provided an active phased array antenna as defined in Claim 4, wherein the open end stab is constituted by laminating a grounded conductor, the ferroelectric, a strip conductor, and the ferromagnetic materials, sequentially.
According to Claim 6 of the present invention, there is provided an active phased array antenna as defined in Claim 4, wherein the open end stab is constituted by laminating the grounded conductor, the ferroelectric, the ferromagnetic materials, and the strip conductor, and the ferroelectrics and the ferromagnetic materials are laminated between the grounded conductor and the strip conductor in a surface direction parallel to the grounded conductor surface.
Therefore, the active phased array antennas defined in Claims 4 to 6 can realize an active phased array antenna which is of a simple structure and enables continuous and wide variations of orientation characteristics with a simple structure.
According to Claim 7 of the present invention, there is provided an antenna controlling apparatus which is molded employing ferroelectrics, ferromagnetic materials, paraelectrics, and electrode materials by an integral molding using ceramics, and the above-mentntioned antenna controlling apparatus is provided with a function of a phase shifter.
According to Claim 8 of the present invention, there is provided an antenna controlling apparatus which is molded employing ferroelectrics, ferromagnetic materials, paraelectrics, and electrode materials by an integral molding using ceramics, and the antenna controlling apparatus is provided with functions of a phase shifter and a dc blocking element.
According to Claim 9 of the present invention, there is provided an antenna controlling apparatus which is molded employing ferroelectrics, ferromagnetic materials, paraelectrics, and electrode materials by an integral molding using ceramics, and the antenna controlling apparatus is provided with functions of a phase shifter, a dc blocking element, and a high-frequency blocking element.
According to Claim 10 of the present invention, there is provided an antenna controlling apparatus which is molded employing ferroelectrics, ferromagnetic materials, paraelectrics, and electrode materials by an integral molding using ceramics, and the antenna controlling apparatus is provided with functions of a phase shifter, a dc blocking element, and a high-frequency blocking element, and an antenna patch.
Therefore, an active phased array antenna which employs the antenna controlling apparatuses defined in Claims 7 to 10 of the present invention can realize an active phased array antenna with a less performance degradation due to accuracy variations at the assembly.
According to Claim 11 of the present invention, there is provided an active phased array antenna as defined in any of Claims 1 to 3, wherein an antenna controlling apparatus as defined in any of Claims 7 to 10 is provided.
According to Claim 12 of the present invention, there is provided an active phased array antenna comprising a row-column array antenna wherein row array antennas, in each of which antenna patches and phase shifters are connected alternately serially, are connected with phase shifters alternately in series, in which there is provided an antenna controlling apparatus as defined in any of Claims 7 to 10.
Therefore, the active phased array antennas defined in Claims 11 or 12 can realize an active phased array antenna which is of a simple structure and capable of continuously changing orientation characteristics.
According to Claim 13 of the present invention, in the active phased array antenna as defined in any of Claims 1 to 12, the grounded conductor is subjected to drawing.
According to Claim 14 of the present invention, there is provided an active phased array antenna as defined in Claim 13, wherein all the feeding lines are provided with a strip conductor comprising a linear conductor having identical sectional shape.
Therefore, the active phased array antenna defined in Claim 13 or 14 can realize a high-gain active phased array antenna without employing an expensive low-loss dielectric material.
According to Claim 15 of the present invention, there is provided an active phased array antenna as defined in any of Claims 1 to 6, or Claim 12, a supporting dielectric material, the grounded conductor, and the strip conductor for feeding are laminated to form the lamination, and this lamination and an antenna controlling apparatus as defined in any of Claims 7 to 10 are molded by an integral molding using ceramics.
Therefore, it is possible to realize a high-performance active phased array antenna in a millimeter wave.